I have some small cracks on the sidewalls of my tires. They are the original tires from 1980. I am not sure if they have "always" been there or if they appeared within the last few months since I was able to get the honda up and running. Is there any tire chemical/cleaner that makes rubber a little more pliable? The treads on the tires look fine. I am just trying to squeak a little more life out of them.